What cultural faux pas should I try to avoid making in Reykjavik?

"When visiting Reykjavik it is important to be respectful and familiarize yourself with Iceland’s culture and customs. In general, it is best to avoid loud and boisterous behavior. As the majority of Icelanders are atheist, it is not considered polite to talk about religion. It is also important to be considerate of the natural environment and refrain from driving off-road and loud ATVs and motorbikes on trails. Additionally, it is important to be respectful of local customs regarding nudity and cultural expression. Taking photos or videos of people in public without their permission is also considered impolite," remarked another expat who made the move to Reykjavik, Iceland.